1. Field of the Invention
The present invention relates to polyurethane/ureas, in particular, aqueous polyurethane/urea dispersions wherein the polyurethane/ureas contain pendant alkoxysilane groups.
2. Description of Related Art
The production of linear or cross-linked solvent-based polyurethane/ureas and aqueous polyurethane/urea dispersions are well known. The solvent-based polyurethane/ureas and the aqueous polyurethane/urea dispersions may be used for a wide range of commercial applications such as adhesives or coatings for various substrates including textile fabrics, plastic, wood, glass fibers and metals. Chemical resistance, abrasion resistance, toughness, tensile strength, elasticity and durability are among the many desirable properties of these coatings.
Regardless of the property level which may be obtained for coatings prepared from commercial polyurethane/ureas, there is a continuing need to improve these properties, in particular water resistance, solvent resistance, weather resistance and physical properties such as abrasion resistance.
It is an object of the present invention to provide polyurethane/ureas, in particular, aqueous polyurethane/urea dispersions, which can be used to prepare coatings that possess these properties and still retain the other valuable properties of the polyurethane ureas.
This object may be achieved in accordance with the present invention by preparing the polyurethane/ureas, in particular, the polyurethane/urea dispersions containing pendant alkoxysilane groups from dihydroxy compounds containing urea and alkoxysilane groups.
Aqueous polyurethane dispersions containing pendant alkoxysilane groups are known and disclosed, e.g., in U.S. Pat. Nos. 4,567,228, 4,582,873 and 5,041,494 and Published Application No. WO 03/11937. However, in these applications the alkoxysilane groups are incorporated through mixed primary/secondary diamines containing alkoxysilane groups instead of dihydroxy compounds containing urea and alkoxysilane groups as required by the present invention. An advantage of incorporating the alkoxysilane groups in accordance with the present invention is that the alkoxysilane groups are incorporated by the formation of urethane groups instead of urea groups as in the prior art. The presence of urethane groups generally results in a product having a lower viscosity than a similar product containing more urea groups.